A border is a defined line that separates two areas, such as countries, states, or regions. It can be marked by natural features like rivers and mountains, or by man-made structures like fences and walls. Borders help establish the limits of political and legal jurisdictions, determining where one authority ends and another begins. Borders can also influence trade, travel, and cultural exchange. They often require documentation, such as passports, for crossing. In some cases, borders can lead to conflicts or disputes, especially when they are not clearly defined or are contested by different groups or nations, such as in the case of Israel and Palestine.